An integrated circuit package provides electrical connections from an integrated circuit chip to external conductors, and protection of the chip from environmental conditions. Additionally, management of thermal dissipation is an increasingly important consideration in the development of packages for many integrated circuit chips. Circuits used in telecommunications and other applications may dissipate power in excess of several Watts. Consequently, it is necessary to provide an integrated circuit package having an efficient method of heat removal. Typically a heat sink for an integrated circuit is provided by mounting the chip in contact with a thermally conductive metal or alloy structure having at least one surface exposed to the ambient environment or to a secondary thermally conductive element for dissipating heat. Thermally conductive structures may be referred to as heat sinks or heat sinks. In those devices requiring high levels of heat dissipation, a heat sink may contact fins to increase the exposed surface area. However, such structures add considerably to the package size, the amount of board space required, and to costs.
With the continued drive towards reducing the dimensions of integrated circuit packages, conventional packaging techniques are severely challenged to provide effective heat dissipation in a readily manufacturable and reliable package.
Surface mounted Ball Grid Array (BGA) packages include external contacts made by an array of solder balls on the bottom of the package. These packages are of considerable interest for many integrated circuit applications because the devices are generally smaller in size and have lower inductance than leaded packages. The substrate for a BGA package may comprise a laminate, a composite, a ceramic, or in the case of smaller packages, a flexible film.
In an increasing number of devices, the chip is encapsulated in a molded plastic with the chip backside attached to a low cost substrate or interposer having low density conductive layers. Flexible tape or low cost laminate substrates typically have very low thermal conductivity and consequently, the IC chip is separated from the PCB by a thermal barrier and from the ambient air by a poorly conductive encapsulation. In particular, in the ever increasing number of BGA devices having lower cost substrates, there is a need for a reliable, readily manufactured package with thermally enhanced performance.